The present invention relates to a device for thermal monitoring for an electrical installation and more particularly a device sensitive to heating of the connection.
There are known electrical installations provided with different safety devices and particularly devices sensitive to increases in the intensity of a flowing current (fusible and disconnectable) and devices for the detection of the loss of current to the ground (differential devices).
Experience has however shown that a number of accidents have taken place by heating of connections in a bad condition. These faulty connections are not protected by present safety devices and are substantially undetectable both by electricians and by the control agencies particularly during the reception of work. This risk is greater because the quality of connections can only deteriorate with time.
The present invention has for its object to overcome these drawbacks by providing a thermal monitoring device which is sensitive to the heating produced by a defective connection.
The present invention thus has for its object a thermal monitoring device for a connection of an electrical installation, characterized in that it comprises a first connecting element in heat and electrical relation with a connection to be monitored, a second connection element in electrical relationship with the ground of the installation, electrical connection means which interconnect the two connection means and which are adapted to have two conditions, namely a first or normal condition of operation in which they are electrically insulated, and a second rupture condition in which they become electrically conductive when they reach a critical temperature.
In one embodiment of the invention, the electrical connection means are such that when they reach the critical temperature, they pass, irreversibly, from a non-conductive condition to a conductive condition.
The connection means could be constituted by a conductive piston in electrical connection with the first connection, which is urged by resilient means toward the second connection, against fusible retention means which melt when the connection to be monitored reaches the critical temperature.
The connection means could also be constituted by an insulating element of the thermoretractable type, whose one surface, called the recto, is in contact with the first connection and the second surface, called the verso, is in contact with the second connection, this element being such that, when the temperature of the connection to be monitored reaches the critical temperature, it retracts thereby exposing a contact surface of the first connection with the second.
In a modification of this embodiment of the invention, the thermal monitoring device comprises an electrical sensor and conductor which is electrically connected to a second connecting element and whose one free end comes into contact with the verso of the thermoretractable insulating element in the contact surface adapted to be exposed.
The thermal monitoring device can be disposed in parallel to the terminals of the connection to be monitored but also can be totally integrated into the latter. In such an embodiment, the first connection element will be constituted by a mechanical constituent of the connection.